The overall objective of this project is to identify and characterize the functions of the mononuclear cells participating in various forms of inflammatory reactions, especially reactions that are immunologically mediated, including delayed hypersensitivity reactions, allografts, autoimmune diseases and tumors undergoing rejection. Infiltrating mononuclear cells are studied in frozen tissue sections through identification of cell surface markers and also in suspension following isolation from reaction sites. In addition, the propensity of purified subpopulations of lymphocytes to emigrate into various types of reactions are being studied. Other studies are aimed at assessing the capacity of lymphocyte subpopulations to initiate cell mediated reactions in vivo following transfer into normal or irradiated recipients, at elucidating the role of antibodies in cutaneous basophil hypersensitivity reactions, and at exploring ways in which glomerular injury can be produced by cell mediated mechanisms.